This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. P2001- 15044, filed on Jan. 23, 2001, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
This invention relates to a press-contact type semiconductor device, and particularly to a press-contact type semiconductor device of a multiple chip module structure having a plurality of semiconductor elements. Further, the invention relates to a technique which is applicable to press-contact type semiconductor devices used to control vehicle motors in the traction applications and power sources.
2. Description of the Related Art
Referring to FIG. 12 of the accompanying drawings, a press-contact type semiconductor device 100 of the related art comprises semiconductor elements 103A and 103B which are sandwiched in a pressed state between a common emitter power source plate (a lower electrode post) 101 and a common collector power source plate (a upper electrode post) 105. The semiconductor elements 103A and 103B are power switching elements such as insulated gate bipolar transistors (IGBT). The semiconductor element 103A has an emitter electrode 131 and a gate electrode 132 on its front surface, and a collector electrode 133 on its rear surface. The same holds true to the semiconductor element 103B. The semiconductor elements 103A and 103B are mounted in the face-down state. In FIG. 12, the emitter electrodes 131 and gate electrodes 132 are under the semiconductor elements 103A and 103B while the collector electrodes 133 are on the semiconductor elements 103A and 103B. In each of the semiconductor elements 103A and 103B, the emitter electrode 131, gate electrode 132 and collector electrode 133 are electrically connected in parallel.
The common emitter power source plate 101 and common collector power source plate 105 are mainly made of copper, a copper alloy or the like which has excellent electric conductivity and thermal conductivity. The semiconductor elements 103A and 103B are made of silicon. A thermal buffer 102 is provided between the common emitter power source plate 101 and the semiconductor elements 103A and 103B considering a difference of thermal expansion coefficients of these materials. Further, another thermal buffer 104 is provided between the common collector power source plate 105 and the semiconductor elements 103A and 103B.
A side cover 106 extends around the common emitter power source plate 101, semiconductor elements 103A and 103B and common collector power source plate 105, and are ceramics insulators or the like in order to avoid electric short-circuiting between the common emitter power source plate 101 and common collector power source plate 105.
With this press-contact type semiconductor device 100, a switching voltage V is supplied to the gate electrodes 132 of the semiconductor elements 103A and 103B from an external power source 110 in order to intermittently introduce a current I to the common emitter power source plate 101 from the common collector power source plate 105.
In the semiconductor device 100, a reference potential of the switching voltage V is an emitter potential. In other words, an external terminal 101P of the common emitter power source plate 101 is connected to a reference potential terminal of the external power source 110, and a circuit operating potential terminal is connected to a gate terminal 132P for supplying the switching voltage V to the gate electrode 132. See FIG. 12. As a result, inductances Ls1 to Ls4 and Lg1 to Lg3 are generated in circuits between the gate electrodes 132 and emitter electrodes 131 of the semiconductor elements 103A and 103B.
The inductances Ls1 and Ls2 apply an induction voltage to the switching voltage V in response to a variation dI/dt of the current I, which causes mal-operations (error operations) of the semiconductor elements 103A and 103B. Further, the inductance Ls1 and Ls2 result in current concentration. The inductances Ls2, Ls3 and Lg1 delay timings for switching on or off the semiconductor elements 103A and 103B, which will lead to power loss. Still further, the semiconductor elements 103A and 103B may operate at varying timings. The inductances Lg2 and Lg3 may cause oscillations between the semiconductor elements 103A and 103B, and vibrate the current I. The inductances Lg2 and Lg3 cause current concentration.
According to the embodiment of the invention, there is provided a press-contact type semiconductor device comprising at least: a plurality of semiconductor elements each of which has a first main electrode and a control electrode on a front surface thereof and a second main electrode on a rear surface thereof; a second common main power source plate having the semiconductor elements positioned on a front surface thereof and electrically connected to the second main electrodes; a first common main power source plate arranged on the front surface of the semiconductor elements and electrically connected to the first main electrodes of the semiconductor elements; a common control signal/main current plate arranged between the semiconductor elements and having at least a common control signal wiring layer electrically connected to the control electrodes and a main current wiring layer electrically connected to the first main electrodes; a conductive connector electrically for connecting at least the main current wiring layer and the first common maim power source plate; and a conductive elastic member configured to connect electrically the main current wiring layer or the first common main power source plate to the conductive connector by elasticity.